Method of making grommets



Oct. 19, 1937. E. ALMDALE METHOD OF MAKING GROMMETS Original Filed April 26, 1935 INVENT OR.

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ATTORNEY.

Patented Oct. 19, 1937 2,096,623 PATENT OFFICE METHOD OF MAKING GBOMMETS Einar Alindale, Detroit, Mich, assilnor to The Midland Steel Products Company, Cleveland, Ohio, a corporation of Ohio Original application April 26, 1935, Serial No. 18.140, Patent 2,054,187, September 15, 1936. Divided and this application June 8, 1986,

SerialNo. 83.240

7 Claims.

This invention relatm to a method of manufacturing grommets and clinch nuts which are adapted to be welded to metal plates whereby parts may be secured to the metal plates by at-. tachment to the grommets or nuts, and is a division of my copending application Serial No. 18,140 filed April 26, 1935.

An important object of the invention is to provide a method for forming welding projections on grommets or clinch nuts for projection-welding to metal plates.

Another important object of the invention is to provide a method by which these grommets can be rapidly and cheaply manufactured from bar stock.

Other objects and advantages of the invention will become apparent during the course of the following description.

In the accompanying drawing forming a part employed to d signate like parts throu hout the several views,

Fig. 1 is a longitudinal sectional view through the apparatus for manufacturing the grommets.

25 Fig. 2 is a bottom elevational view of one form 35 grommet produced in the apparatus of Fig. 1

and shown attached to a plate, and

Fig. 7 is a bottom elevational view of this modified form of grommet.

The grommet or nut I0 shown in Figs. 2 and has a head or body portion of any desired shape herein shown as being polygonal or square. The base or lower face of the nut is provided with an integral centrally disposed circular pilot l2 which has a central threaded opening it extending axially therethrough as well as through the head or. body of the nut. The opposite ends of this threaded opening I2 are countersunk as at it to facilitate assembly of the parts therewith. The pilot I! is preferably of a height less than the thickness of a metal plate or part to which it is to be attached as shown in the modification in Figs. 4 and 6. The pilot may, if desired, be of such dimensions as to cause its outer end to be fiush with the metal plate after the nut has been welded to the plate around the perforation therein.

To facilitate projection welding of the nut to the plate, the base of the body portion thereof is provided at its corners with integral triangular projections it which are not as tall as the pilot of the description and wherein like numerals are jections ii are tapered as at II to merge into the base of the nut as illustrated. I

The apparatus for manufacturing this nut is shown in Fig. 1 and comprises a punch press having a stationary die provided with a plurality of die holes 2!, 22, 23, 2t and 25, all of which are intersected by a passage 26 extending longitudinally through the die 20 for the slidable reception of a bar or sheet 21 of cold rolled steel or other suitable metal from which the nuts are to be formed. Any suitable mechanism can be employed for manually or automatically feeding thebarstock2'l stepbystepinthe 28 with respect to the die holes.

Reciprocally mounted with respect to the stationary die 20 is a reciprocating head or ram III to which various forming tools ll, 22, 22, 84 and 25 are clamped by a suitable clamping member it fastened to the ram 20 by bolts or other suitable means not illustrated. These forming tools are each axially disposed with respect to the die holes as shown in Fig. 1.

In order to produce the nuts, one end of the barstoclr 2Iisfirstfedinto the passage 28a sufiicient distance so that the punch 3i will perforate a hole in the bar stock a sufiicient distance from the end thereof for the first nut to be produced. Upon elevation of the reciprocating ram 2| the bar stock 21 is moved a step. a distance corresponding substantially to the width of the nut to be produced, to thereby place the initially perforated nut between the tools II and 22, and upon downward movement of the ram 20, the punch 2i perforates a hole in the second nut to be produced. The next successive feeding step places the first formed perforation in alignment with the pilot 22 so that the latter enters the first formed perforation upon the next descent of the ram 20, and at the same time the punch 2| perforates another opening in the bar stock 21 which opening will be the hole in the third nut to be produced. The next two successive feeding steps of the bar stock causes the first formed perforation to be aligned with the pilot I! of the coining tool 32, which upon the next descent of the ram 30 provides the projections II and pilot i2 with the countersink it in the adjacent end of the nut, and simultaneously therewith, the countersink at the opposite end of the opening I! by means of a countersink tool 28 disposed in the opening 23 of the die 20. After completion of the coining operation and upon two successive feeding steps of the bar stock 21 the first formed aperture is aligned with the cutting tool 84 to shave and clean up the first formed hole upon the next down stroke of the ram 30.' The next two successive feeding steps of the bar stock 21 through the passage 26 brings the first formed perforation in alignment with the pilot 39 of the cutoff tool so that upon the next downstroke of the ram 30. the end of the bar stock is cut off along the dotted line ill to form the first clinch nut, whereby thereafter and upon each downstroke of the ram, a nut is formed and ejected through the passage 25 into a suitable hopper. The nut is also threaded in a suitable threading machine. The forming tools may be so spaced with respect to each other so as to. eliminate the two successive feeding steps required to bring the first formed nut into position with respect to the forming tools, that is, only one reciprocation of the ram 3 0-will be necessary to feed the bar stock 21 for each successive forming operation. In the method herein described, a nut is produced upon each reciprocation of the ram after the first formed nut has been produced.

Variousother forms of grommets or nuts may as pilot l2 hereinbefore described. In this modification the welding projection assumes the form of an annular welding rib 52 concentric with the pilot 5| and spaced therefromas illustrated at 53. The nut is welded to the plate 54 by inserting the pilot 5! in the aperture 55 and the annular welding rib 52 is fused to the metal plate 54. In order to form the welding rib 52 the coining tool 33 is provided with an appropriate coining surface.

Figs. 6 and '7 illustrate another modified grommet or nut adapted to be produced by the apparatus of Fig. 1 and comprises a pilot 3i similar to the pilot l2 which is surrounded with an annular welding rib 62 chamfered at an angle of nuts may be resorted to without departing from approximately 46 degrees to meet the base of the nut and cause the welding rib to terminate in a V-shaped edge which is fused into the metal plate 63 surrounding the perforation 64 therein. The welding rib 62 is formed in the apparatus shown in Fig. 1 by asuitably shaped coining tool 33.

In the twomodifications shown in Figs. 4 through 7 the annular welding ribs are fused into the metal plates so as to form a liquid or air tight seal with the plates.

It is to be understood that the nuts may be threaded or unthreaded and various changes in the steps of the method and the shape and arrangement of various parts of the grommets or the spirit of the invention or the scope of the appended claims.

I claim:

1. A method of forming grommets from continuous bar stock consisting of feeding. a bar in successive steps through apunch press, each feeding step taking place as the punch elevates, perforating the stock on the first descent of the punch, piloting a member through the perforation on a subsequent step while perforating the stock for another grommet, forming a pilot and projections around the first perforation with a pilot therein whileperforming the preceding steps on other portions of the stock.

2. A method of forming grommets from continuous bar stock consisting of feeding a bar in successive steps through a punch press, perforating the stockon one step for one grommet, forming a pilotandprojections around the first perforation with a pilot therein on a subsequent step while perforating the stock for another grommet.

3. A method of forming grommets from continuous bar stock consisting of feeding a bar in successive steps through a punch press, perforating the stock on one step for one grommet, forming a pilot and a projection around the first perforation with a pilot therein on a subsequent step while perforating the stock for another grommet, and cutting off a portion of the stock subjected to the preceding steps while performing the preceding steps on other portions of the stock.

4. A method of forming grommets from continuous bar stock consisting of feeding a bar in successive steps through a punch press, perforating the stock on one step for one grommet, forming a projection around the first perforation with a pilot therein on a subsequent step while perforating the stock for another grommet, and cutting off a portion of the stock subjected to the preceding steps while performing the preceding steps on other portions of the stock.

5. The step in the method of forming a grommet consisting of subjecting a perforated body of cold rolled steel to a coining tool having a pilot which is moved into the perforation while the tool compresses portions of the body lengthwise of the perforation to form a depression leav ing a pressed up collar around the perforation and projections spaced from the collar, thereby forming a highly worked grommet having con= densed grain structure.

6. The method of forming grommets from continuous bar stock consisting of feedingthe bar in successive steps through a slot in the die of a punch press, each succeeding feeding step to advance the stock taking place as the punch ele= vates, perforating the stock on the first descent of thepunch, feeding the stock the width of one grommet, perforating the stock on the next descent of the punch and each subsequent descent thereof, extending a pilot through the first perforation on the next descent of. the punch, feed ing the stock through the slot the width of two grommets and entering a pilot in the first formed perforation while a coining tool compresses portions of the grommet lengthwise of the perforation to form a depression leaving a pressed up perforation made, after which the stock is moved the width of two grommets and the nrst perforated grommet is severed from the bar while substantially the ninth grommet is being perforated.

7. The step in the method of forming a grommet consisting of subjecting a perforated body of metal to a coining tool havinga pilot which is moved into the perforation while the tool compresses portions of the body lengthwise of the perforation to form adepression leaving upstanding projections spaced from the perforation, thereby forming a highly worked grommet having condensed grain structure. 

